This invention relates to adjustable telescopic connections, and more particularly to an integral twist lock arrangement for telescoping tubes.
Axially adjustable telescoping tubes are regularly utilized to provide a desired axial length. The difficulty generally arises when providing a suitable arrangement for locking the telescoping tubes at the desired axial position so as to prevent further sliding therebetween. Numerous types of locking arrangements have been heretofore provided in the prior art. However, none of them have provided sufficient ease of utilization and at the same time minimal cost and avoidance of complex manufacturing steps.
By way of example, U.S. Pat. No. 958,752 describes telescoping tubes with the outer tube provided at its end with an eccentric lip and the inner tube is provided at its end with an eccentric annular body. The eccentric annular body is movable with the inner tube within the outer tube. Once the desired axial position is arranged, the inner tube is rotated along with the annular body to provide a jamming position between the inner and outer tubes.
One of the problems with this prior art arrangement is that the strength of the jamming arrangement varies with the amount of telescopic overlap. Also, at the location where the annular body is jammed, there is only one bearing contact between the inner and outer surfaces so that the inner tube will be considerably bent. Additionally, it is necessary to provide a separate annular body, such as a sleeve or ring, around the inner tube which requires additional manufacturing steps and adds to the cost of the arrangement.
Another locking arrangement is described in U.S. Pat. No. 2,871,044 which includes side wedges forming eccentric surfaces on the inner tube. A roller is caused to climb onto one of these eccentric surfaces to effect a tightening of the inner and outer tubes. The roller is held in place by a covering sleeve over the outer tube. This arrangement requires additional parts, extensive manufacturing steps, and only permits limited axial sliding between the tubes.
A further arrangement for locking telescoping tubes is provided in U.S. Pat. No. 642,193 which requires a spiral groove of a varied depth in conjunction with a spiral key which rides within the groove. U.S. Pat. No. 3,419,293 utilizes a cylindrical plug with an eccentric portion and a complex collar arrangement for engaging the eccentric plug. Similarly, U.S. Pat. No. 4,195,346 utilized an eccentric plug, which is engaged between the inner and outer tubes and requires two additional sleeves for operating the locking arrangement.
It is accordingly noted that although prior art locking arrangements have been provided for telescoping tubes, most of these arrangements required additional parts, complex manufacturing steps, and provided for difficult manipulations in order to achieve secure locking between the telescoping parts.